CN114786635A

CN114786635A - Medical article for preventing decubitus ulcers

Info

Publication number: CN114786635A
Application number: CN202080086319.4A
Authority: CN
Inventors: 阿克赛尔·埃克施泰因; 玛雅·克尔默
Original assignee: Paul Hartmann AG
Current assignee: Paul Hartmann AG
Priority date: 2019-12-19
Filing date: 2020-12-17
Publication date: 2022-07-22
Also published as: DE102019135061A1; WO2021123028A1; EP4076314A1; US20230049297A1

Abstract

The invention relates to a medical article (10) for preventing the appearance and/or progression of decubitus ulcers, comprising a press cloth (12) and a skin contact layer (13) adhered to the skin to be treated, wherein the press cloth (12) has a proximal surface and a distal surface and comprises a core (15) and a shell (14) surrounding the core (15), wherein the core (15) has a proximal surface and a distal surface and comprises a nonwoven material formed from fibers and absorbent particles, wherein the press cloth (12) has a longitudinal direction with a first modulus of elasticity and a transverse direction with a second modulus of elasticity and the first modulus of elasticity is greater than the second modulus of elasticity.

Description

Medical article for preventing decubitus ulcers

The present invention relates to medical articles for use in the prevention of the development and/or progression of decubitus ulcers.

Decubitus ulcers (synonyms: decubitus ulcers, pressure sores, decubitus ulcers or respectively decubitus ulcers) are defined as a nutritional imbalance of tissues (mainly skin and subcutaneous tissues) due to the compression of blood vessels and ischemia by external (long-term) pressure effects, with cellular necrosis, maceration, and eventual infection. Decubitus ulcers occur primarily in bed rest, particularly in body positions where the skin lies directly against the bone, but also, for example, in cases where the prosthesis fit is poor and the plaster bandage is too tight.

The bedsore is divided into the following stages. Decubitus ulcers in stages II, III and IV are considered chronic wounds here:

stage I: is a persistent, enveloping type of red swelling of the skin that persists even after the pressure is removed. The red and swollen edges are clear and may harden or have excessive temperature. The skin is not damaged.

Stage II: blisters and skin abrasion are formed during this stage and thus a partial loss of skin occurs. A portion of the epidermis up to the dermis is damaged. Superficial wounds or flaked sores were present at this stage.

Stage III: in this further development stage, loss of all skin layers can be observed. In addition, subcutaneous tissue damage and eventual cellular necrosis can be observed, which may be deep and underlying muscle tissue. Empirically, the necrotic tissue must first be bounded (abgrenzong) until the entire extent of tissue damage becomes discernable. Decubitus ulcers III are clinically manifested as open, deep sores.

Stage IV: loss of all skin layers and extensive destruction of muscles, bones or ancillary structures (tendons, joint capsules), tissue necrosis or damage can be recorded in this most dangerous phase. Bedsores IV are clinically manifested as large areas of open and deep sores.

Decubitus ulcers may occur when pressure is applied to soft tissues such that blood flow is completely or partially interrupted in those tissues. The shear forces arising from friction against a particular skin site also contribute significantly to the development of decubitus ulcers. Such shear forces are generated by the movement of skin over other material surfaces, such as bed sheets. When the skin of a patient is displaced by the shear forces occurring against the tissue located below the skin, the blood vessels located in these tissues are likewise pressed together, so that the blood flow in these tissues is restricted or interrupted. Decubitus ulcers are preferentially present at specific skin locations, such as at the skin overlying the sacral region, coccyx, heel, or hip. Other locations where decubitus ulcers often occur are the elbows, knees, joints, shoulders. Decubitus ulcers occur in most cases on patients whose movement is severely affected or completely interrupted, such as bedridden patients or patients who rely on essentially wheelchairs. In these patients, the ability to relieve pressure by voluntary movement of the limb of the patient under pressure is limited. Other factors may also play a significant role in the development of decubitus ulcers, such as a lack of protein, adverse microenvironment (skin moisture due to perspiration, wound exudate or incontinence), vascular diseases such as arteriosclerosis, or diseases that limit skin sensitivity such as paralysis or neuropathy. The cure rate for decubitus ulcers can be very limited due to the age of the patient, the medical condition of the patient, smoking or medication.

It is often difficult to successfully avoid the development of decubitus ulcers or to prevent the deterioration of existing decubitus ulcers in susceptible patients. Common measures include dispersing pressure by frequently changing the patient's position or designing a bunk or wheelchair with a pressure reduction mattress or pillow.

The mechanisms responsible for the appearance of decubitus ulcers are not fully understood. Since pressure and shear forces acting on the skin and tissue contribute to the development of decubitus ulcers, measures for preventing the development or worsening of decubitus ulcers should be focused on reducing these values.

It would therefore be desirable to provide products which are effective in preventing the occurrence of decubitus ulcers by the application of these products. It would also be desirable to provide products by which the exacerbation of already occurring decubitus ulcers can be prevented.

The invention according to claim 1 solves the above mentioned problems.

In the present application, the term "proximal surface" is understood to mean the side of a layer or sublayer that faces towards the skin covered by the article, while the term "distal surface" refers to the side that faces away from the skin. If there is a planar extension in the broadest sense in the component parts of the medical article of the present invention described below, such component parts have a proximal surface and a distal surface, respectively. These faces are bounded at their sides. If the term "in all directions (allseigig)" is used within the scope of the present application, this is to be understood as meaning all sides defining the surface of one sublayer or layer.

The medical article according to the present invention comprises a press cloth and a skin contact layer adhered to the skin to be treated. The press cloth comprises a core and a shell surrounding the core. The core comprises a nonwoven material formed of fibers and absorbent particles. The press cloth has a longitudinal direction with a first modulus of elasticity and a transverse direction with a second modulus of elasticity. Here, the first elastic modulus is greater than the second elastic modulus.

In a preferred embodiment, the shell comprises a first sublayer formed of a liquid permeable material disposed on the proximal surface of the core and a second sublayer formed of a material different from the material of the first sublayer of the shell disposed on the distal surface of the core. Here, a first partial layer of the shell extends beyond the proximal surface of the core in all directions and a second partial layer of the shell extends beyond the distal surface of the core in all directions, so that the first partial layer of the shell and the second partial layer of the shell each form an edge region which surrounds the core in all directions. The first part-layer of the shell and the second part-layer of the shell are connected to one another in this edge region.

For the sake of clarity of explanation, it is mentioned that the terms longitudinal direction and transverse direction should not be understood in the following manner: the medical article according to the invention has a greater longitudinal extension in one of these two directions than in the other direction. Medical articles according to the present invention may also have a substantially square or circular shape.

Within the scope of the present invention, the anisotropy of a layer or a sublayer is understood to mean that its mechanical properties behave differently depending on the measurement direction. In the sense of the present invention, the anisotropic layer or sublayer preferably has an anisotropy with respect to its elastic modulus. The layer or sub-layer preferably has a longitudinal direction with a first modulus of elasticity and a transverse direction at right angles to the longitudinal direction with a second modulus of elasticity, wherein the first modulus of elasticity is greater than the second modulus of elasticity.

The longitudinal direction of the press cloth preferably corresponds to a direction at right angles to the machine direction of the method of producing the medical article, while the transverse direction corresponds to a direction parallel to the machine direction of the method of producing the medical article.

The core has a proximal surface and a distal surface. The core comprises a nonwoven material formed of fibers and absorbent particles. The material may comprise any kind of wound exudate absorbing material, in particular absorbent fibres and absorbent particles. Such materials fulfil a dual function in the article of the invention, as a favourable cushioning effect may be exhibited due to the fibre-containing structure and a favourable contribution to improving the microenvironment at the relevant skin site due to the absorbent particles. Moisture, for example due to skin respiration, perspiration or wound exudate exudation, can thus be absorbed by the particles. As explained above, the outflow of liquid at the skin surface promotes an increase in the shear forces between the skin surface and the material against the skin, whereby the creation of new decubitus ulcers or the worsening of existing decubitus ulcers may be promoted. The article according to the invention eliminates this risk due to the absorption of liquid.

The material comprises in a suitable manner a mixture of absorbent fibres and absorbent particles. The nonwoven sublayer formed from fibers and absorbent particles fulfills the double function mentioned here in a special manner when the absorbent particles are distributed substantially homogeneously in the nonwoven material formed from fibers. Upon absorption of liquid, the absorbent particles swell and form the following structure: the structure forms a connection with the surrounding fibres and thus constitutes a network-like composite of fibres and gel particles which are particularly suitable for deflecting pressure and shear forces away from the skin surface and the tissue lying thereunder.

Suitable materials for the absorbent fibres may be, for example, cellulose or cellulose-based polymers, viscose, polyesters, polyamides and derivatives, copolymers and mixtures thereof. Also suitable are fibers which have superabsorbent properties and are based on polyacrylic acids, sodium polyacrylates, polyacrylates and derivatives, copolymers and mixtures thereof. The preferred material is cellulose.

Suitable materials for the absorbent particles include cellulose derivatives, alginates, carboxymethylcellulose and derivatives, copolymers, mixtures and salts thereof, and superabsorbent particles including polyacrylic acid, sodium acrylate, acrylates and derivatives, copolymers and mixtures thereof.

In a preferred embodiment, the core of the press cloth comprises a mixture of absorbent fibres and superabsorbent material. The absorbent fibers serve to rapidly absorb wound exudate, while the superabsorbent material serves to have a high absorbent capacity. Suitable absorbent fibers may be cellulose-based materials. In a preferred embodiment, the absorbent fibers consist essentially of cellulose fibers. Suitable superabsorbent materials are present in particulate form.

In a preferred embodiment, the core of the press cloth comprises a mixture of absorbent fibres, which consist essentially of cellulose, and superabsorbent particles, which comprise polyacrylic acid and sodium polyacrylate. Such cores serve to rapidly absorb moisture, particularly wound exudate, and to rapidly distribute the moisture in the core.

The superabsorbent material may be included within the core of the press in an amount of from 1 wt% up to 99 wt%. The amount of superabsorbent material preferably forms a proportion of 30 to 55% by weight of the core of the press cloth.

In theory, the term "superabsorbent material" is understood to mean water-insoluble swellable polymers which are capable of absorbing and binding several times their own weight in liquid (such as water, saline solutions or body fluids, e.g. wound exudate). As a result of the absorption of the liquid, a hydrogel is formed. The absorption capacity for pure water is generally greater than the absorption capacity for saline solutions or body fluids. In connection with the present invention, the term "superabsorbent material" is understood as meaning a w-value having a free swelling capacity corresponding to the standard measurement method WSP240.2(05) of at least 10g/g, preferably at least 20 g/g. Measurement Methods for determining the w value WSP240.2(05) are described in Standard Test Methods for non-woven and Related Industries, 2008 edition (published by the International Association of non-woven and Related Industries and Industries, EDANA, International Association Serving the non-woven and Related Industries, and british, brussel, belgium, published by the non-woven Industry Association (INDA, Association of non-woven fabrics textile Industries, inc.) of the north carolina, usa.

In a preferred embodiment, the core of the press cloth has a thickness of 100g/100cm according to the test method described in example 4 itself²To 5000g/100cm²Preferably 120g/100cm²To 4000g/100cm²Particularly preferably more than 130g/100cm²To 3000g/100cm²The absorption capacity of (2).

The core is surrounded by a shell. A shell is understood to be an element that completely surrounds the core. The shell may be made up of one or more sublayers. Here, the individual sublayers may extend beyond the surface of the core. The part of the partial layer which protrudes beyond the core can be oriented in a planar manner and can then form the edge region of the protruding core. Alternatively, the part of the sub-layer which protrudes beyond the core may wrap around the edge of the core material in the protruding area, so that the core material is wound by this material section.

In a preferred embodiment, the shell comprises a first sublayer formed of a liquid permeable material having hydrophilic properties. The material may include a material having a hydrophilic characteristic due to its chemical nature, or a material having an inherently hydrophobic characteristic due to its chemical nature and treated in a chemical or physical process to make its surface hydrophilic. Suitable methods for hydrophilizing an otherwise hydrophobic material include electrochemical processes, flame treatment, corona treatment and plasma treatment.

Suitable materials for the first part-layer of the shellThe materials are cellulose, polyester, polyamide, polyethylene, polypropylene and copolymers formed from two or more of the above materials. The first sub-layer of hydrophilic material preferably comprises a polypropylene nonwoven which has been physically treated so that its surface exhibits hydrophilic properties or comprises a basis weight of 37g/m²Comprises 55% polyamide fibres and 45% viscose fibres. Such materials are available under the model number M1526 from Freudenberg (germany). Alternatively preferred is a fiber with 45g/m comprising 63% polypropylene fibers and 37% viscose fibers²A nonwoven fabric of weight per unit area obtainable under model 670532/2 of Freudenberg (germany).

In a preferred embodiment, the shell comprises a second sub-layer formed from a material having hydrophobic properties. The hydrophobic character of the material may be due to its chemical nature or comprise a material that has an inherently hydrophilic nature but is altered by chemical or physical treatment (e.g., by treatment with a fluorohydrocarbon, silicone, alkane, etc.) such that it exhibits hydrophobic properties. Suitable base materials for the second part-layer of the shell are cellulose, polyester, polyamide, polyethylene, polypropylene and copolymers formed from two or more of the above materials.

In a preferred embodiment, the first sublayer of the shell comprises a first material having hydrophilic properties and the second sublayer of the shell comprises a second material having hydrophobic properties.

In another preferred embodiment, the second sublayer of the shell comprises a substantially liquid-impermeable material.

The two sublayers of the shell surrounding the core in all directions can be designed to be of any color. Medical articles are usually white, which represents purity and sterility. In another embodiment, at least one of the two sublayers has a pale green color. This color produces a strong color contrast when the sublayer is wetted with liquid, so that the caregiver can identify the medical article attached to the patient directly by external observation when the core contains liquid or when the maximum absorbent capacity of the article has been reached. The presence of liquid or the amount of liquid absorbed within the core of the article according to the invention gives a clear indication that a decubitus ulcer has just appeared in the area of the skin covered by the article or that the extent of the decubitus ulcer covered by the article has changed. It has been surprisingly determined that the green color corresponding to RAL6019 ensures a particularly advantageous color contrast with wound exudate and is also perceived as clean and sterile by patients and caregivers at the same time.

The first and second sublayers of the shell of the core are connected to each other. Such joining may be achieved by any suitable process for joining materials, whether direct or indirect.

In a preferred embodiment, the first and second part-layers of the shell each comprise a material having thermoplastic properties. The first and second partial layers of the shell can then be connected to one another in a thermal method step. The thermal joining process can be carried out in a continuous manner and is therefore less expensive to use than other processes. Suitable thermal methods for joining the materials include thermal welding, laser welding, and ultrasonic welding.

In a preferred embodiment, the second sub-layer of the shell comprises a thermoplastic material having hydrophobic properties and the first sub-layer of the shell comprises a thermoplastic material as follows: the thermoplastic material is the same material as the second sublayer of the shell and is treated in a chemical and/or physical process to make it hydrophilic. When the first material and the second material have different chemical properties, the physical characteristics may also be significantly different from each other. This may have an adverse effect in the connection method where the following conditions must be present: these conditions must be compatible with all materials involved. In a thermal joining process, the operating temperature must be above the melting point or melting range of each of the individual materials involved. However, the thermolabile material may decompose at an excessively high temperature. Therefore, it may be very disadvantageous to select a suitable material for the first and second sub-layers depending on the chemical nature of the material. When the first and second sub-layers comprise materials of the same chemical nature, these materials do not differ in their physical properties in relation to the implementation of the connection method. This is particularly advantageous in the thermal joining process when the processing temperature is only slightly above the melting temperature of the materials participating therein. The risk of thermal decomposition is thus significantly reduced.

In a preferred embodiment, the thermoplastic material of the first and also of the second part-layer of the shell comprises polypropylene.

In a preferred embodiment, the first and second partial layers of the shell surrounding the core are connected to one another in a thermal process and therefore have a welded connection to one another. The welded connection formed by the thermal joining method has an advantageous connection due to its welding strength and flexibility. Within the scope of the present invention, the weld strength refers to the force required to separate the sub-layers connected to one another. The weld strength can be measured by the method described in the examples of the present application. In a preferred embodiment, the weld strength is greater than 0.75N/15mm, preferably greater than 1N/15 mm.

High weld strength is advantageous to prevent accidental delamination of the materials connected to each other. Delamination of the first and second sub-layers of the shell may itself to a lesser extent lead to leaks inside the article. In this case, additional shear forces may occur within the article which further contribute to the appearance or worsening of decubitus ulcers.

Flexible in the sense of the present invention means that the material is capable of changing its properties of configuration. Flexibility is described by the stiffness of the material.

For medical articles, flexibility is important in order to fit the body surface of the patient (often irregular). Furthermore, inflexible bandages are very stiff and cause pressure and stress on the skin surface of the patient when moved, which may cause pain and may contribute to the appearance or worsening of decubitus ulcers.

In a preferred embodiment, the welded connection comprises at least one discontinuous weld line. The discontinuous weld lines represent an advantageous flexibility which positively influences the wearing comfort for the patient and prevents the occurrence or the worsening of decubitus ulcers.

In a preferred embodiment, the welded connection comprises four to six parallel discontinuous weld lines, which has an effect on the favourable balance of properties of weld strength and flexibility.

In a preferred embodiment, the at least one discontinuous weld line is oriented parallel to the machine direction during production.

Furthermore, the press cloth may comprise a diffusion layer. Such layers can achieve a rapid distribution of moisture, in particular wound exudate, in the horizontal direction inside the core of the press cloth. This layer may be located on the proximal surface of the core between the proximal sublayer of the shell and the proximal surface of the core. The diffusion layer may also be a material sublayer that encases the entire core. The diffusion layer is preferably a paper layer that completely surrounds the core. In a preferred embodiment, the paper is made of cellulose and has a mass of 15 to 20g/m²Weight per unit area of (c).

The skin contact layer adhering to the skin to be treated comprises a material with a skin-friendly adhesive. Suitable adhesives may be based on acrylates, polyvinyl ethyl ether, polyurethanes, silicones, derivatives, mixtures or copolymers thereof, for example as described in GB 1280631. Preferably a pressure sensitive adhesive.

In a preferred embodiment, the skin contact layer adhering to the skin to be treated comprises a sub-layer of skin-friendly silicone gel. The silicone adhesive is suitably a so-called soft skin adhesive silicone elastomer. The total coating mass of the silicone adhesive is suitably 15g/m²To 500g/m²Preferably 50g/m²To 250g/m²Particularly preferably 100g/m²To 200g/m²。

Surprisingly, it has been found that such medical articles have advantageous properties with respect to adhesion to skin. Methods for determining adhesion to skin will be described in the examples of the present application. Suitable medical articles must be capable of adhering to the skin without loss of adhesion, so that application of the article can be guaranteed in a few hours, preferably for several days, particularly preferably for at least three days, most preferably for seven days. On the other hand, the article must have skin-friendly properties, which allow the article to be removed after successful application without causing pain or skin irritation to the patient. Surprisingly, it has been found that articles having an adhesion of 200mN/cm, preferably 350mN/cm and 650mN/cm are advantageous in this respect.

In a preferred embodiment, the skin contact layer adhered to the skin to be treated comprises openings allowing wound exudate to reach the core. These openings can have any geometric shape, regular or irregular, in particular circular, elliptical, triangular, square, pentagonal, hexagonal or other polygonal shapes with equal or unequal side lengths.

In a preferred embodiment, the skin contact layer adhering to the skin to be treated comprises an opening of arbitrary shape, said opening having a diameter of 0.03mm²Up to 7.0mm²Average open area of (a).

In a preferred embodiment, the skin contact layer adhering to the skin to be treated has openings with a total open area of between 10% and 25% of the total surface area of the skin contact layer. It has surprisingly been found that open neps in this range give the preferred wound exudate absorption rate. Within the scope of the present invention, the absorption rate refers to the time required to absorb wound exudate. The absorption rate can be determined by the test methods described in the examples of the present application. Surprisingly, it has been found that the absorption speed is particularly advantageous when the skin contact layer adhering to the skin to be treated has an open area of 11% to 22%, preferably 12% to 18%. Suitably, the density of openings is between 1000 and 1000000 openings per square meter, for example between 5000 and 50000 openings per square meter.

In a preferred embodiment, the skin contact layer adhering to the skin to be treated comprises openings of substantially circular shape having an average diameter between 0.2mm and 3.0 mm. Surprisingly, it has been found that the absorption speed is advantageous when the skin contact layer adhering to the skin to be treated has openings of circular shape and an average diameter of 2.2mm to 2.8 mm.

Although it is possible to provide a skin contact layer which essentially consists of a soft skin-adhesive silicone elastomer which adheres to the skin to be treated, it is preferred that this skin contact layer comprises an additional sublayer of material having openings which correspond to the openings of the silicone adhesive layer without closing these openings. The material provided with openings may comprise any type of medically acceptable material, including textile materials such as non-woven, hook, knit or woven. In a suitable manner, the material having openings is a homogeneous material, such as a polymer mesh or a perforated membrane. Suitable polymeric materials include polyethylene, polypropylene, polyester, polyvinyl acetate, ethylene vinyl acetate, and polyurethane. In a suitable manner, the sublayer material has a thickness of 1 μm to 100 μm, preferably 5 μm to 50 μm.

The skin contact layer adhered to the skin to be treated may be provided with a medically acceptable adhesive layer on its distal side. Such an adhesive layer provides a particularly stable connection between the skin contact layer adhering to the skin to be treated and the distal side of the article which is arranged in the constituent part of the skin contact layer adhering to the skin to be treated (in particular the press cloth and/or in the edge region of the outer part-layer). The adhesive is preferably a pressure sensitive acrylate adhesive.

The preferred material of the sublayer of the skin contact layer adhering to the skin to be treated is 150g/m²Has a silicone adhesive layer, which may be referred to by the name

Obtained from the company ASC (france).

In a preferred embodiment, the article according to the invention has an additional outer sublayer, wherein said outer sublayer has a water vapor permeable and substantially liquid impermeable film material.

This additional outer sublayer supports and stabilizes the press cloth and forms a barrier to microorganisms passing through the article. The additional outer part-layer is substantially liquid-impermeable, butIs permeable to water vapor. The additional outer part-layer preferably has a film material. The additional outer sublayer has a thickness of 300 to 30000g/m measured according to EN 13726²24h, preferably 1000 to 15000g/m²24h and in a particularly preferred embodiment 1000 to 5000g/m²Water vapor transmission rate of 24 h. The additional outer part-layer has a thickness of 10 μm to 500 μm, preferably 15 μm to 300 μm, particularly preferably 20 μm to 100 μm.

The additional outer sub-layer may have various geometrical shapes, such as square, rectangular, circular, oval, trapezoidal or polygonal, preferably with rounded corners.

The additional outer sublayer has a proximal surface and a distal surface. The distal surface preferably has a low surface friction. By using a material with a lower surface friction on the distal surface of the outer part-layer, shear forces occurring when in contact with the surface of another object (e.g. a bed sheet, mattress or pillow) and which may contribute to the occurrence or worsening of decubitus ulcers are reduced.

Suitable materials for this additional outer sub-layer are polyurethane, polyalkoxyalkylacrylate, methyl acrylate, as disclosed in GB 1280631. In a suitable manner, the outer sublayer has a continuous layer of high-density polyurethane foam with substantially closed cells (Zellen). A suitable material is a 30 μm thick polyurethane film available under Coveris corporation model 1305.

This additional outer sublayer is preferably transparent in order to enable viewing of the press cloth. This is advantageous when assessing the condition of the skin area covered by the article. In particular, it is possible to identify at an early stage whether the state of the skin region lying below the article deteriorates during the course of the treatment.

In a preferred embodiment, the proximal surface of the additional outer part-layer has a coating with a pressure-sensitive adhesive and projects beyond the distal surface of the press cloth in all directions, so that the additional outer part-layer forms an adhesive edge region which surrounds the press cloth in all directions.

The adhesive secures this additional outer part-layer to the other layers of the article, in particular to the press cloth and to the skin contact layer which is adhered to the skin to be treated. The additional outer sublayer may be coated continuously or discontinuously or in part with adhesive on its proximal side. The additional outer sub-layer may be continuously coated with adhesive, which means that the adhesive covers the entire proximal side of the additional outer sub-layer with adhesive. In another embodiment, the adhesive may be applied in stripes, dots, or different patterns. In another embodiment, the additional outer sub-layer comprises an adhesive layer on its proximal side, which adhesive layer provides an adhesive-free area in the middle of the additional outer sub-layer in order to reduce contact with the distal surface of the press cloth. The water vapor permeability in the adhesive-free region is thus increased. When the press cloth starts to swell due to absorption of moisture, its spatial extension changes. This aspect can lead to delamination due to shear forces within the article. More importantly, however, the shear forces that occur apply stress to the skin covered by the article and may then contribute to the further appearance or worsening of decubitus ulcers. In addition, it has the advantage that it reduces the skin moisture which contributes to the development of decubitus ulcers. An article providing an adhesive free region between the distal surface of the compress and the proximal surface of the additional outer sub-layer may be advantageous in this respect.

The adhesive is preferably a pressure sensitive adhesive of the type commonly used in medical bandages. Suitable pressure sensitive adhesives may be based on acrylates, polyvinyl ethyl ether, polyurethanes, silicones, derivatives, mixtures or copolymers thereof, for example as described in GB 1280631. The weight per unit area of the amount of adhesive applied is suitably 10g/m²To 100g/m²Preferably 15g/m²To 50g/m²Particularly preferably 20g/m²To 30g/m²。

Surprisingly, it has been found that medical articles according to the present invention, illustrated in the examples of the present application, have advantageous properties in the absorption rate test.

Surprisingly, it has been found that the medical article according to the invention has advantageous properties in terms of the balance between adhesion to the skin and absorption speed.

The additional outer part-layer, the press cloth and the skin contact layer adhering to the skin to be treated can have different or identical extensions.

In a particular embodiment, the distal surface of the press cloth is covered by the additional outer part-layer. The additional outer part-layer has an extension in two planar directions which is larger than the plane of the distal surface of the press cloth, while the press cloth and the skin contact layer, which is adhered to the skin to be treated, are coextensive. The outer part-layer thus forms an edge region which completely surrounds the press cloth. This type of article is also known as the insert type ("island type").

In a particular embodiment, the distal surface of the press cloth is covered by the additional outer part-layer. The additional outer part-layer has an extension in both planar directions which is greater than the plane of the distal surface of the press cloth. The outer part-layer thus forms an edge region which extends beyond the press cloth in all directions. The skin contact layer, which adheres to the skin to be treated, has an extension in two planar directions which is greater than the plane of the proximal surface of the press cloth. This skin contact layer thus constitutes an edge region which extends beyond the press cloth in all directions. Here, the skin contact layer is coextensive with the outer sublayer. This type of product is also known as sandwich type ("sandwich type").

The medical article, the additional outer sub-layer, the core of the press cloth, the shell and the skin contact layer adhered to the skin to be treated can each have any suitable size and geometry, in particular square, rectangular, circular, oval, polygonal. If the geometry of any of these sub-layers has corners, these corners may preferably be rounded. This reduces the risk of the article curling during use and delaminating from other sub-layers or the skin. In a preferred embodiment, the radius of the rounded corners is 5mm to 15mm, preferably 12.5 mm.

The medical article according to the invention may have at least one cover layer covering the proximal surface of the skin contact layer adhering to the skin to be treatedOr a bonding area. The cover layer covers and protects the press cloth and prevents premature adhesion of the adhesive part of the article. The cover layer may include a film formed of polyethylene, polypropylene, fluorocarbon, and paper coated with the above materials or silicone. A suitable material may be a polyethylene foil having a thickness of 100 μm, which may be selected from

The company obtains it.

The medical article according to the invention can be applied to a skin area of a patient and fixed by means of a skin contact layer contained in the article which adheres to the skin to be treated and thereby protects the skin area against contact with external materials (e.g. bed sheets). The occurrence of shear forces, which typically occur due to friction between the skin of the patient and the outer material, is thus avoided. Because the medical article according to the invention has a certain rigidity, the frictional forces occurring between the outer part-layer of the article and the outer material are not transmitted through the layers of the article to the skin surface covered by the article. Thus, the article according to the invention can reduce or even avoid shear forces at the skin area at risk. The friction occurring between the outer part-layer of the article and the outer material can be estimated by measuring the coefficient of friction. The static friction coefficient is different from the dynamic friction coefficient, the static friction coefficient represents the adhesion friction between two materials, and the dynamic friction coefficient represents the sliding friction between the two materials. It is important that neither the static nor the dynamic coefficient of friction exceed a certain value in order to minimize the risk of shear forces occurring in the skin area covered by the article. The coefficient of friction depends on humidity. Skin surfaces that are wetted by sweat or exudates are more sensitive to the presence of harmful shear forces than dry skin surfaces. Also, a determinant as to the suitability of the article is whether the exterior surface of the article retains its friction reducing properties even under elevated humidity. Surprisingly, it has been found that a static coefficient of friction and a dynamic coefficient of friction of 0.20 to 0.50, preferably 0.25 to 0.45, are advantageous. The static friction coefficient and the dynamic friction coefficient may be determined according to the method described in example 9 of the present application.

Medical articles according to the present invention may also help reduce the pressure applied to a particular skin area and the underlying tissue. Pressure is created by the force acting on an area (e.g., the weight of a body part acting on the skin surface in contact with external material such as bed sheets beneath the body part). Since medical articles can achieve a pressure reduction, the forces that can act on the skin area must be borne by the article and distributed over a larger area.

For this purpose, the article material must have a certain compressibility. A material that is too compressible conducts the pressure acting on the surface further directly in the direction of the pressure without distributing the force significantly over a larger area. In contrast, materials that are very compressible are only subjected to small pressures. The compressibility of the article according to the invention can be determined according to the method described in example 8 of the present application. Compressibility is defined by the degree of shrinkage of the article at a certain force. The compressibility is also dependent on humidity. Surprisingly, it has been found that an article having a shrinkage of 2.0 to 5.0mm, preferably 3.0 to 4.5mm, particularly preferably 3.5 to 4.0mm, under a force of 150N in the dry state and a shrinkage of 2.0 to 6.0mm, preferably 3.0 to 5.0mm, particularly preferably 4.0 to 4.5mm, under a force of 150N in the wetted state is advantageous for preventing the appearance and the worsening of decubitus ulcers.

The medical article also helps to reduce the shear forces that occur when the medical article has different moduli of elasticity in different directions of extension. The modulus of elasticity is a material characteristic value in materials technology, which describes the proportional relationship between mechanical stress and elongation at solid deformation in linear elastic behavior. Mechanical stress is a measure of the internal stress of an object due to external loading of the object (e.g., due to pressure and/or shear forces). A material layer having a greater modulus of elasticity in a first direction than in a direction at right angles thereto can, with a certain stability, resist forces acting parallel to the first direction and yield in a direction at right angles thereto. An article having a higher modulus of elasticity in a direction parallel to the action of an external, pressure-exerting force or shear force than in a direction at right angles thereto may contribute to deflecting the emerging force from its initial force action from the skin covered by the article and the tissue lying thereunder, so that the appearance or worsening of decubitus ulcers may be reduced. The ratio of the elastic moduli in the different directions, i.e. the degree of anisotropy, is in particular decisive here. The modulus of elasticity can be determined in the cyclic tensile test described in example 7 of the present application. Surprisingly, it has been found that an anisotropy of from 1.5 to 20.0, preferably from 2.0 to 10.0, particularly preferably from 2.5 to 8.0, is advantageous for preventing the appearance or worsening of decubitus ulcers.

In a preferred embodiment, the medical article according to the present invention has two or more sublayers, which have such anisotropy. Each of the partial layers has a longitudinal direction with a first modulus of elasticity and a transverse direction parallel to the longitudinal direction with a second modulus of elasticity, wherein the first modulus of elasticity is greater than the second modulus of elasticity. In this case, when the two or more sublayers are oriented in the medical article such that the longitudinal direction of a first such anisotropic sublayer and the longitudinal direction of a second such anisotropic sublayer, and where appropriate the longitudinal direction of other such anisotropic sublayers, are oriented parallel to each other, the anisotropic effects of the respective sublayers are in common effect complementary in an advantageous manner.

In another embodiment, a medical article according to the present invention has an element adapted to identify the direction of a material having a higher modulus of elasticity. Such elements may be provided to identify and understand the element by visual, audible, or tactile sensations of the article user. Such elements may be positioned anywhere on the article so long as the information is understandable. Such an element is preferably arranged on one of the outer sides of the article. Elements that can be recognized by visual perception include, for example, colored markers, geometric symbols, characters, written content, or combinations thereof. The element identifiable by tactile sensation comprises, for example, an imprint, a protrusion or a depression of one or more of the materials used in the article, which can be identified, for example, by tactile sensation. The identification of different material directions can also be achieved by using materials with different surfaces in different directions, the surface differences of which can be recognized by tactile sensation. Particularly preferred is a marking in the form of a visually or tactilely perceptible arrow, the arrow direction of which is oriented along the preferred direction of application on the body surface to be treated. The article according to the invention particularly preferably has a marking in the form of an arrow which is arranged parallel to the longitudinal axis of the body of the patient to be treated, the tip of the arrow pointing in the direction of the head of the patient. For application to body positions that cannot be uniquely determined in relation to the longitudinal body axis of the patient, an identification of the article according to the invention in the form of an arrow is suitable, the tip of which points in the direction of the pressure action that is to be expected with the greatest probability.

A pressure sensitive mattress may provide information, i.e. how pressure is present in the mattress below the skin surface. They do not give information about the pressure relationship inside the affected tissue. The biological mechanisms leading to the appearance or worsening of decubitus ulcers can be simulated and studied by means of simulations using the Finite Element Method (FEM).

Based on FEM simulations, it has surprisingly been found that medical bandages according to the present invention are capable of preventing the occurrence or worsening of decubitus ulcers when applied to skin locations that are generally prone to the occurrence of decubitus ulcers.

The medical article described above is therefore suitable for preventing the appearance of decubitus ulcers. In this case, the article is placed on the still intact skin site, which is threatened in particular by the occurrence of decubitus ulcers.

The medical article is also suitable for application to a skin site where a decubitus ulcer has occurred. These locations are unique especially in open skin wounds that exude wound exudate more or less strongly. In the case of improper treatment, there is a risk in such decubitus ulcers that their state deteriorates in continuous progress. In this case, the preparation is suitable for the prophylaxis and therapeutic treatment of already occurring decubitus ulcers. Since the article not only has liquid-absorbing properties but also reduced pressure and shear forces, the article according to the invention is particularly suitable for this application.

The invention also comprises the article according to the invention for use in applications for preventing the appearance of decubitus ulcers.

The invention also comprises a product according to the invention for use in an application for preventing exacerbation of an already existing decubitus ulcer.

The invention additionally comprises the article according to the invention for use in therapy in the treatment of an already existing decubitus ulcer.

The invention also comprises the use of a medical article according to the invention for the preparation of a medical product for the prevention of the appearance of decubitus ulcers.

The invention also comprises the use of a medical article according to the invention for the preparation of a medical product for the prevention of exacerbation of already existing decubitus ulcers.

FIG. 1 shows a medical article in a top view according to a preferred embodiment of the present invention.

Figure 2 shows the article of figure 1 in a cross-sectional view along section line a-a of figure 1.

Figure 3 shows a type 5A sample according to DIN ISO 527 and its characteristic dimensions as used for cyclic tensile testing according to example 7.

Fig. 4 shows a graph showing the result of FEM calculation. The abscissa shows the von mises stress occurring on the skin. The ordinate shows the associated contrast volume (volume of interest, VOI) with von mises stress, which is at least as large as the associated abscissa segment.

Fig. 1 shows a top view of a medical article (10) according to the invention with an additional outer sublayer (11) and a compress (12). The skin contact layer, which is adhered to the skin to be treated, is arranged on the side facing away from the observer. The press cloth (12) comprises a core (15) and a shell (14) surrounding the core (15). The shell (14) comprises a proximal first sub-layer (facing away from the viewer) of liquid permeable nonwoven material and a distal second sub-layer (14b) of substantially liquid impermeable nonwoven material. The proximal part-layer of the shell (14) covers the proximal side of the core (15) and protrudes beyond the proximal side of the core (15), wherein an edge region (16) is formed which surrounds the core (15) in all directions. A distal sublayer (14b) of the shell (14) covers and protrudes beyond the distal side of the core (15), wherein an edge region (16) is formed which surrounds the core (15) in all directions. The proximal part-layer of the shell (14) and the distal part-layer (14b) of the shell (14) have been connected to one another along an edge region (16) surrounding the core (15) by means of a heat treatment and thus have a welded connection (18). The welded connection (18) is formed by five discontinuous welding lines (19). The outer partial layer (11) extends beyond the press cloth (12), wherein an edge region (17) is formed which surrounds the press cloth (12) in all directions.

Fig. 2 shows a cross-sectional view of the medical article (10) according to the invention of fig. 1 along the sectional line a-a of fig. 1 with a press cloth (12), an additional outer sub-layer (11) and a skin contact layer (13). The press cloth (12) comprises a core (15) and a shell (14). The shell (14) is composed of a proximal sublayer (14a) and a distal sublayer (14 b). The skin contact layer (13) consists of a sublayer formed of perforated planar material (13a) and a sublayer of skin-friendly silicone gel (13 b). The outer part-layer (11) consists of a polyurethane film material having a thickness of 30 μm, having low friction properties, being permeable to water vapour and impermeable to liquids. The outer sub-layer (11) is coated with an acrylate based adhesive layer (not shown). The core (15) comprises a mixture of cellulose fibres and particles of superabsorbent sodium polyacrylate in a pre-formed air-laid (Airlaid) material. The core (15) furthermore comprises a diffusion layer (not shown) in the form of a sub-layer of cellulose paper placed around the non-woven sub-layer formed by the mixture of cellulose fibres and polyacrylate particles. The proximal sub-layer (14a) of the shell (14) is a non-woven material formed from a mixture of viscose and polyamide fibres. The distal sub-layer (14b) of the shell (14) is a nonwoven material formed from polypropylene fibres. A proximal sublayer (14a) of the shell (14) covers the proximal side of the core (15) and protrudes beyond the proximal side of the core (15), wherein the proximal sublayer forms an edge region (16) which surrounds the core (15) in all directions. The distal part-layer (14b) of the shell (14) covers the distal side of the core (15) and protrudes beyond the distal side of the core (15), wherein an edge region (16) is formed which surrounds the press cloth (12) in all directions. The proximal part-layer (14a) of the shell (14) and the distal part-layer (14b) of the shell (14) are connected to each other along their edge regions (16) surrounding the core (15). The perforated planar material (13a) of the skin contact layer (13) consists of a polyurethane film having circular openings (13 c). These openings (13c) have a uniform shape with an average diameter of 2.4mm and are arranged in a regular pattern, resulting in an open area ratio of 15%. The outer part-layer (11) extends beyond the press cloth (12). The skin contact layer (13) extends beyond the press cloth (12), wherein an edge region (17) is formed which surrounds the press cloth (12) in all directions. The outer sub-layer (11) and the skin contact layer (13) are coextensive.

Fig. 3 shows samples with corresponding dimensional values as were used for determining the material properties (tensile strength) in the experiment according to example 7.

Fig. 4 shows an image of the stress (measured in kPa) occurring in the relevant model volume (volume of interest, VOI). The ordinate here gives what proportion of the relevant volume has a stress corresponding at least to the abscissa value associated with the corresponding curve point. Curve (a) shows the stress occurring at the skin in the relevant contrast volume when applying the inventive subject matter according to example 1. Curve (D) shows the stresses that occur in the relevant comparison volume without further protective measures. Curves (B) and (C) show the stresses that occur in the relevant contrast volumes in the case of two different races.

Examples

Example 1: medical article

The medical article includes a compress, an additional outer sublayer, and a skin-contacting layer adhered to the skin to be treated. The press cloth comprises a core and a shell. The shell is composed of a proximal sublayer and a distal sublayer. The skin contact layer consists of a perforated planar material and a skin-friendly silicone adhesive sublayer. The outer part-layer consists of a polyurethane film material having low friction properties and a thickness of 30 μm, which is permeable to water vapour and impermeable to liquid. The core comprises a mixture of cellulose fibres and particles of superabsorbent sodium polyacrylate in a pre-formed airlaid material. The core furthermore comprises a diffusion layer in the form of a sublayer of cellulose paper which has been placed around the airlaid mixture formed by cellulose fibres and polyacrylate particles. The proximal sublayer of the shell is a nonwoven material formed from a mixture of viscose and polyamide fibers. The distal sublayer of the shell is a nonwoven material formed from polypropylene fibers. The perforated planar material of the skin contact layer consists of a polyurethane film with circular openings. These openings have a uniform shape with an average diameter of 2.4mm and are arranged in a regular pattern so that the open area ratio is 15%. The skin contact layer additionally comprises a skin-friendly silicone adhesive sublayer without closing the openings of the perforated planar material.

Example 2: test solution for characterizing medical bandages

Solution A (salt solution)

2L of deionized water

0.74g calcium chloride dihydrate (CaCl)₂·2H₂O，CAS：10035-04-5)

16.6g sodium chloride (NaCl, CAS: 7647-14-5)

Solution B (exudate solution)

1l of deionized water

70g Albumin from Chicken (CAS: 9006-59-1)

0.2g allura red AC (CAS: 25956-17-6)

9g sodium chloride (NaCl, CAS: 7647-14-5)

0.37g calcium chloride dihydrate (CaCl)₂·2H₂O，CAS：10035-04-5)

2g methyl 4-hydroxybenzoate (CAS: 99-76-3)

1g propyl 4-hydroxybenzoate (CAS: 94-13-3)

Example 3: absorption speed

The absorption rate of the article is determined by the time required for complete absorption of the test liquid. The test solution may be a salt solution (solution a) or an exudate solution (solution B). These solutions, as well as these samples, must be preconditioned at room temperature prior to testing by holding these samples and solutions at 22 ℃ for two hours.

Fill a 50mL burette with the test solution. The liquid level was fixed at 15 mL. The sample is placed under a burette with the skin-facing surface facing the burette when the article is in use. The distance between the burette and the sample was fixed at 1 cm. The burette valve was opened and a stopwatch was started. Where 2mL of the test solution is discharged from the burette. The stop watch is stopped once 2mL of the test solution has been completely absorbed by the article, that is to say when the drops of test solution no longer remain on the perforations of the skin contact layer. If the sample is large enough, 1 to 3 measurements can be made on the same article. Here, the test positions are the center and two further points along the diagonal of the product in the direction of the corners, the positions of these points corresponding to the shape of the number 3 on a common die.

At least five samples were studied.

Each value is classified in the following way:

time(s)	[0 to 4.9 ]]	[5.0 to 10.9 ]]	[11.0 to 30.9 ]]	[31.0 to 60.0%]	>60
						Categories	Immediate use	Very quickly	Quickly taking away	Average out	Slowly, slowly

The article according to the invention is combined with commercially available bandages

silicone、

Life、

Border performs the comparison.

Absorption speed

Example 4: absorption capacity

The solution used (saline solution or exudate solution) as well as the sample must be preconditioned at room temperature prior to testing by holding it at a temperature of 22 ℃ for two hours.

Determination of the basic mass m of the article after removal of the protective layer covering the skin contact layer₁. The length and width of the core of the press cloth are measured, whereby the surface area S of the core of the press cloth can be obtained. The housing is filled with a test liquid. The mass of the test solution should be at least 40 times greater than the mass of the article. The article was dipped into the dish while a stopwatch was started. The side of the article facing the skin during use should face the bottom surface of the dish and the back of the article should be placed upwards. The article should not adhere to the bottom surface of the dish. The preparation was left to stand in the dish for 30 minutes +/-1 minute. The bandage should only contact itself at its edges and not at the core of the press cloth. The bandage was fixed in the jig at the corners and allowed to hang at room temperature for 20 minutes. Determination of the wetting Mass m of the product₂. Amount m of test solution absorbed_{Liquid for medical purpose}Calculated in the following way:

m_{liquid for treating urinary tract infection}＝m₂-m₁

The absorption capacity is the quotient of the amount of test solution absorbed divided by the surface area S of the core of the press cloth, in g/100cm²Is a unit.

Absorption capacity (m)₂-m₁/S)*100

silicone、

Life、

Border performs comparisons.

Comparison of absorption capacity:

example 5: adhesive capacity

The purpose of the study was explained to the testers and the testers expressed consent in written form. The test products were applied to the back of each individual tester (two samples per test product): one sample of each test product was placed on the top half of the back. The second sample was placed in the lower half of the back.

The lower end of each sample was folded at a distance of 0.5cm from the lower edge to provide a starting point for peeling off the sample from below to above with a universal testing machine. The samples were applied by trained personnel and pressed onto the skin of the test person by means of a metal roller (1kg, five reciprocal rolls).

The tester came to the study site 3 hours 50 minutes after sample application and stayed in the tempered chamber for at least 10 minutes. The test subjects were checked for the absence of sweating. The samples were peeled off 4 hours after application of the samples with the aid of a universal testing machine to determine the adhesive capacity.

General test machine: zwick 1120 (Zwick ltd, urm, germany). The universal testing machine measures the force required to peel the sample from the skin of the test subject. To peel the sample, the tester is left in a sitting position. The sample was peeled off at an angle of approximately 135 °. One measurement was taken for each sample and two samples were studied for each product.

Example 6: strength of welding

Cell strength at 50N

Weld strength measurements were performed using a tensile tester equipment MTS C42.503E (MTS systems, meadow steppe, usa).

The sample was prepared by blanking out a portion of the core of the cloth press, which portion contained the weld line and had a rectangular shape with a width of 15mm and a length of 25mm, with the 15mm side corresponding to the weld line. The sample must be removed at least 2mm away from the corner of the product. The core material is removed after blanking so that only a sheet of two nonwoven materials connected to each other remains. The grips of the test equipment were placed so that the distance therebetween was 2 cm. The two nonwoven sheets are held in separate holders. The test apparatus was started at a speed of 200mm/min until the two nonwoven sheets were separated from each other.

The weld strength is the average strength over the test period. Given in N/15 mm.

Example 7: tensile strength

Sampling

Samples corresponding to type 5a according to DIN ISO 527 were punched out of the investigated product, the properties of which are reproduced in fig. 3. The dimensions correspond to the following values:

l₁	length of narrow parallel portion	25±1
			l₃	Total length of the track	≥75
b₁	Width of narrow part	4±0.1
			b₂	Width at the end	12.5±1
r₁	Shorter radius	8±1
			r₂	Longer radius	12.5±1
L	Initial distance of the clamp	50±2
			L₀	Measuring length	20±0.5

The sampling was not only in the direction extending parallel to the machine direction of the preparation process, but also in the direction extending at right angles to the machine direction of the preparation process.

Cyclic tensile test

The mechanical properties of the punched out samples were investigated in cyclic tensile tests at a test temperature of 35 ℃ with the aid of a universal testing machine with a temperature chamber of type Z005 from Zwick/Roell. The samples were stretched twice until a nominal elongation of 15% and then relieved of load and subsequently tested until break.

Experiment was carried out

The force and deformation strokes were measured in tensile experiments and force-stroke graphs of the different samples studied are presented.

The elastic modulus is defined as the slope of the image in the stress-elongation plot:

modulus of elasticity E ═ sigma/epsilon

Where the stress is σ and the elongation is ε.

Here, σ ═ F/a denotes the mechanical stress per cross-sectional area of the sample.

In this case,. epsilon. DELTA.l/l₀Denotes the elongation, wherein the change in length Δ l-l₀Where l represents the length of the sample after the tensile test and l₀Representing the original length of the sample.

Not only a sample sampled in a direction extending parallel to the machine direction of the preparation method but also a sample sampled in a direction extending at right angles to the machine direction of the preparation method was investigated. The elastic modulus thereof was divided to calculate the anisotropy of the corresponding material.

The anisotropy in terms of elastic modulus of the various constituents of the medical article according to example 1 obtained in this way is detailed in the following table:

position of	Anisotropy of property
		Outer sub-layer	1.1
Press cloth	2.5
		Nonwoven material	3.7
Distal sublayer of shell	2.4
		Skin contact layer	0.9

Example 8: compression

Cyclic compression experiment

The mechanical properties were investigated by means of a universal testing machine with a temperature chamber, model Z005 from Zwick/Roell, drying and wetting the product with water in a cyclic compression test at a test temperature of 35 ℃. The sample was compressed twice up to a force of 150N and then unloaded and then tested up to a maximum of 450N.

Experiment was carried out

Example 9: coefficient of friction

Friction test

The tribological behaviour of the samples against cotton surfaces in the dry and wet state was investigated with a rotary tribometer.

Wetting out means that the sample is applied to the cover layer at the surface with 0.15ml/cm²The distilled water of (2) is wetted. An amount of water corresponding to the area of the sample was applied to the patch surface by means of a dropper and allowed to penetrate for one hour, and then the test was performed. For this purpose, the samples were bonded to a stationary flat steel surface (diameter 60 mm). The rotating counter-running body is a cotton fabric which is bonded to a steel punch die (diameter 60mm) by a double-sided adhesive tape. The sample and the counter running surface were pressed against each other with a contact force of 50N, and then the friction coefficient between the sample and the rotating counter running surface was measured at different speeds.

The drive motor rotates at different defined rotational speeds, which correspond to a sliding speed of 1mm/s to 100 mm/s. The slip velocity was calculated over a 30mm mean diameter.

Experiment was carried out

Test conditions of Friction test

The medical bandages studied had the following coefficient of friction (COF):

example 10: finite Element Method (FEM)

FEM is a general computer-aided numerical method applied under different physical task settings. Logically, FEM is a numerical solution based on a complex system formed by differential equations. FEMs divide large problems into a number of smaller parts, so-called finite elements. Each individual one of these elements is used for analysis and in the overall conclusion the solution of the whole problem is derived.

The working steps of the FEM can be described as follows:

1. creating a 2D or 3D model consisting of finite elements;

2. defining material properties of the model;

3. defining boundary conditions and loads for applying the model to the problem;

4. solving the problem in a computer-aided manner; and

5. the results are analyzed by visualization and calculation.

The FEM calculation on which the invention is based is performed according to the method described in the following document: levy a, Schwartz D, Gefen a, the directional bias in stiffness contributes to the utility of prophylactic sacral dressings in protecting healthy and diabetic tissue from crush injury: computational modeling studies (The distribution of a directional prediction of The effects of a pharmacological scientific study in a protective theory and a pharmacological properties from a compressive study), Int Wound J2017; doi: 10.111/iwj.12821.

To understand the effect of the medical bandage according to the invention, an FE model of the human pelvis and bandage was created. The effect of pressure and stress on the skin and deep tissues was analyzed.

MRI scans of volunteer female testers are used as a basis for the pelvic model in order to ensure the highest possible anatomical accuracy of the model.

The FE model includes 3,900,000 nodes.

Soft tissue behaves as a nonlinear material, where muscle is generalized as a material and fat and skin are generalized as compressible materials, respectively. Bones are classified as rigid bodies.

The modeling is based on the following material properties:

bed: linear modulus of elasticity E of 50kPa

Bone: linear modulus of elasticity E7000 MPa

Adipose tissue: super elasticity (new hooke) C10 ═ 0.0004

Muscle tissue: super elasticity (new hooke) C10 ═ 0.000225

Skin: super-elasticity (new hooke) C10 ═ 0.004

A relevant model volume (volume of interest, VOI) of dimensions 6.7cm x 2.0cm x 5.1cm (x direction x y direction x z direction) is formed, including the sacrum (Os sacrum) and the soft tissue (including skin) beneath it.

Von mises stress refers to a hypothetical uniaxial stress that creates a hypothetical equivalent of a material stress (e.g., an actual multiaxial stress state) based on certain mechanical or mathematical indices of the material.

By means of von mises stress, the actual, generally three-dimensional stress state in the component under solid or flowing conditions can be compared with characteristic values from uniaxial tensile experiments (material characteristic values, for example tensile limit or tensile strength).

Von mises stress can be described according to the following equation:

where σ_I、σ_IIAnd σ_IIIThree spatial directions in which principal stresses occur.

Of particular interest are the stresses occurring in the relevant model volume at the skin, since the stresses responsible for the occurrence and progression of decubitus ulcers and shear forces occur there.

Comparisons between the following calculations were made, respectively: wherein the medical article according to the invention is arranged at the same skin location as in the case where the medical article is not arranged.

Of critical significance is the 10% value. This value gives what maximum stress occurs in up to 10% of the relevant comparison volume. This value corresponds to the curve point belonging to the vertical coordinate segment at 10% VOI.

By comparison of the von mises stress at the skin in the relevant model volume with or without the medical article placed, it can be assumed that it is suitable for preventing the occurrence of decubitus ulcers if the 10% value of the occurring stress experiences a reduction of more than 10%.

The curve shown in fig. 4 has the following 10% value:

curve (a): 21.8239kPa articles according to the invention

Curve (B): 24.3311kPa race 1

Curve (C): race 2 at 24.2884kPa

Curve (D): 27.2725kPa with no product placed

As can be seen from fig. 4, by applying the medical article according to the invention, the 10% value of the von mises stress occurring at the skin in the relevant model volume can be reduced by 20%.

Claims

1. A medical article (10) for preventing the appearance and/or worsening of decubitus ulcers, comprising a compress (12) and a skin-contact layer (13) adhered to the skin to be treated, wherein the compress (12) has a proximal surface and a distal surface and comprises a core (15) and a shell (14) surrounding the core (15), wherein the core (15) has a proximal surface and a distal surface and comprises a nonwoven material formed from fibers and absorbent particles, wherein the compress (12) has a longitudinal direction with a first modulus of elasticity and a transverse direction with a second modulus of elasticity and the first modulus of elasticity is greater than the second modulus of elasticity.

2. The medical article (10) according to claim 1, wherein the shell (14) comprises a first sublayer and a second sublayer, the first sublayer being formed of a liquid permeable material arranged on the proximal surface of the core (15), the second sublayer being formed of a material arranged on the distal surface of the core (15) that is different from the material of the first sublayer of the shell (14), wherein the first sublayer of the shell (14) exceeds the proximal surface of the core (15) in all directions and the second sublayer of the shell (14) exceeds the distal surface of the core (15) in all directions, and wherein the first sublayer of the shell (14) and the second sublayer of the shell (14) form edge regions (16) respectively, which surround the core (15) in all directions, wherein the first sublayer of the shell (14) and the second sublayer of the shell (14) are in phase with each other in the edge regions (16) And (4) connecting.

3. Medical article (10) according to one of the preceding claims, characterized in that the core (15) has a side according to example 4100g/100cm measured by test method²To 5000g/100cm²The absorption capacity of (2).

4. Medical article (10) according to one of claims 2 to 3, characterized in that a first sub-layer of the shell (14) comprises a first material having hydrophilic properties and a second sub-layer of the shell (14) comprises a second material having hydrophobic properties.

5. Medical article (10) according to one of claims 2 to 4, characterized in that the first and second sub-layers of the shell (14) each have a material with thermoplastic properties.

6. The medical article (10) according to claim 5, wherein the second sub-layer of the shell (14) comprises a thermoplastic material having hydrophobic properties and the first sub-layer of the shell (14) comprises a thermoplastic material of: the thermoplastic material is the same material as the second sub-layer of the shell (14) and is treated in a chemical and/or physical process to make it hydrophilic.

7. Medical article (10) according to one of claims 5 to 6, characterized in that the first sublayer of the shell (14) and the second sublayer of the shell have been joined to one another in a heat treatment and thus have a mutual welded connection (18).

8. Medical article (10) according to claim 7, characterized in that the welded connection (18) comprises at least one discontinuous welding line (19).

9. The medical article (10) according to claim 8, wherein the welded connection (18) comprises four to six parallel discrete weld lines (19).

10. Medical article (10) according to one of claims 8 or 9, wherein the at least one discontinuous welding line (19) is oriented parallel to the machine direction during production.

11. Medical article (10) according to one of the preceding claims, characterized in that the skin contact layer (13) adhering to the skin to be treated has a sub-layer of skin-friendly silicone glue (13 b).

12. Medical article (10) according to one of the preceding claims, characterized in that the skin contact layer (13) has openings with a total open area of between 10% and 25% of the total surface area of the skin contact layer (13).

13. Medical article (10) according to one of the preceding claims, wherein the skin contact layer (13) has an opening (13c) of substantially circular shape having an average diameter between 0.2mm and 3.0 mm.

14. Medical article (10) according to one of the preceding claims, characterized in that the article has an additional outer sublayer (11) having a proximal surface and a distal surface, wherein the additional outer sublayer (11) has a water vapour permeable and substantially liquid impermeable film material.

15. Medical article (10) according to one of the preceding claims, characterized in that the proximal surface of the additional outer sublayer (11) has a coating with a pressure sensitive adhesive and the additional outer sublayer (11) exceeds the distal surface of the compress (12) in all directions, such that the additional outer sublayer forms an adhesive edge region (17) surrounding the compress (12) in all directions.

16. Medical article (10) according to one of claims 1 to 14, characterized in that the additional outer sub-layer (11) exceeds the distal surface of the compress (12) in all directions and the skin contact layer (13) is coextensive with the outer sub-layer (11).

17. The medical article (10) according to any one of the preceding claims, wherein the article (10) has an element adapted to identify the direction of the material having the higher modulus of elasticity.

18. A medical article (10) according to one of the preceding claims for use in the prevention of the appearance and/or progression of decubitus ulcers.

19. Use of a medical article (10) according to one of claims 1 to 17 for the preparation of a medical product for the prevention of the appearance and/or the worsening of decubitus ulcers.